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SD card reader not working in Windows

DeviceInBox editorial team · Last updated October 6, 2026

A card reader that stopped working has a short list of causes: the reader has no driver and sits under Other devices, the driver is there but the reader was put to sleep for power saving, or the card itself is at fault. Built-in readers on laptops are PCI Express devices from Realtek, O2Micro or Genesys; readers in USB hubs and dongles are USB devices, and the two need different drivers.

Device Manager showing a Realtek PCIE CardReader under Memory technology devices
A working built-in reader appears under Memory technology devices.

Is the reader there at all?

Insert a card first: some readers only appear once a card is in. Then check Device Manager under Memory technology devices, Universal Serial Bus controllers and Other devices. A reader without a driver shows up as Base System Device, Unknown device or SD Host Controller.

Read its hardware ID (how). The common ones:

Hardware IDDeviceDrivers
PCI\VEN_10EC&DEV_5227RTS5227 PCI Express Card Reader10
PCI\VEN_10EC&DEV_522ARTS522A PCI Express Card Reader10
PCI\VEN_10EC&DEV_525ARTS525A PCI Express Card Reader10
PCI\VEN_10EC&DEV_5229RTS5229 PCI Express Card Reader3
PCI\VEN_1217&DEV_8621Integrated MMC/SD controller18
PCI\VEN_1217&DEV_8620Integrated MMC/SD controller20
USB\VID_0BDA&PID_0129RTS5129 Card Reader Controller21
USB\VID_05E3&PID_0751microSD Card Reader9
Four steps from inserting a card to a working reader
Insert a card first: some readers only appear when one is in.

The power saving trap

Realtek readers are the usual suspects here: the reader works after a restart and is gone after the laptop sleeps.

  1. Properties of the reader, Power Management tab, clear "Allow the computer to turn off this device to save power".
  2. In Control Panel, Power Options, Change plan settings, Change advanced power settings, open PCI Express, Link State Power Management, and set it to Off for both battery and mains.
  3. Restart and test with a card inserted and the lid closed once.
Advanced power settings with PCI Express link state power management set to Off
Aggressive link power management switches built-in readers off.

Rule out the card

  • Try a second card. A card that fails in two readers is the problem.
  • Check the physical lock switch on full-size SD cards. In the lock position the card mounts read-only or not at all.
  • Open Disk Management (Win + X): a card that appears there with no drive letter only needs one assigned.
  • Cards over 32 GB are usually exFAT. Very old readers and card firmware handle SDXC badly; in that case the card works in a USB reader but not in the built-in one.
Disk Management showing a card with no drive letter assigned
A card without a letter is mounted but invisible in Explorer.

Reinstall the driver

  1. Right-click the reader, Uninstall device, tick the option to remove the driver, restart.
  2. If Windows installs a generic SD Host Controller driver and the reader is slow or unstable, install the vendor package for the ID instead.
  3. On laptops, install the chipset package before the reader driver. The reader hangs off a chipset bridge, and without the chipset INF files Windows may not even enumerate it.

USB readers and hubs

USB card readers use the standard mass storage class and need no driver at all. When one does not work, the cause is the port, the cable or the hub, not a missing package. See USB device not recognized. Readers built into monitors and docks sit behind an internal hub, so check that the hub itself is listed under Universal Serial Bus controllers.

Related: Base System Device and Code 10.

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